CN113285230A - Reflective super surface for millimeter wave MIMO and space power synthesis - Google Patents
Reflective super surface for millimeter wave MIMO and space power synthesis Download PDFInfo
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- CN113285230A CN113285230A CN202110430380.2A CN202110430380A CN113285230A CN 113285230 A CN113285230 A CN 113285230A CN 202110430380 A CN202110430380 A CN 202110430380A CN 113285230 A CN113285230 A CN 113285230A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
Abstract
The invention discloses a reflective super surface for millimeter wave MIMO and space power synthesis, which comprises a square reflective super surface main body; the reflection-type super-surface main body comprises NxN reflection-type super-surface units; n is an integer greater than 2; each unit comprises a first metal patch, a first dielectric substrate and a first metal back plate which are sequentially arranged from top to bottom and is of a three-layer structure; the first metal patch is a square metal patch; a first metal patch is arranged on the top surface of the first dielectric substrate; the whole bottom surface of the first dielectric substrate is covered with a first metal back plate; for each reflective super-surface unit at different positions of the reflective super-surface body, the reflective phase response meets the preset caliber phase distribution condition. The reflection type super surface can reflect electromagnetic wave beams with different incident directions through the same reflection type super surface, generates reflection wave beams with the same direction, and verifies that the reflection type super surface can flexibly regulate and control electromagnetic waves.
Description
Technical Field
The invention relates to the technical field of super-surface and patch antennas, in particular to a reflective super-surface for millimeter wave MIMO and space power synthesis.
Background
At present, the metamaterial draws wide attention of society due to the outstanding wavefront regulation capability, and is rapidly developed. However, equivalent parameters, a complex three-dimensional structure and high material loss, which are difficult to achieve by the metamaterial, make it difficult to be applied to practical production.
The super surface, as a two-dimensional metamaterial, has a thickness in one direction of a sub-wavelength size, so that the regulation mechanism of the metamaterial on electromagnetic waves is not limited by the equivalent medium theory of the three-dimensional metamaterial.
In 2011, a super surface based on gradient phase is proposed, which realizes abnormal reflection and refraction of reflected electromagnetic waves, i.e. generalized snell's law of reflection and refraction. The super surface based on the gradient phase consists of a plurality of super surface units, the super surface units are arranged according to reflection or transmission phase responses of gradient change in one or more directions of the super surface, and when electromagnetic waves enter the super surface, the electromagnetic waves have phase abrupt change of a gradient change rule, so that abnormal reflection and refraction of the incident electromagnetic waves are realized. After the gradient phase super surface appears, the strong and free regulation and control capability of the gradient phase super surface to electromagnetic waves attracts the attention of the scientific community. After that, researchers realize perfect conversion from space waves to surface waves, perfect transmission of electromagnetic waves and simultaneous regulation and control of amplitude and phase of the electromagnetic waves in a wide frequency band based on the design idea of the gradient phase super surface.
At present, a Multiple Input Multiple Output (MIMO) technology, as a key technology of 5G millimeter waves, has become a research hotspot at present. The MIMO technology can increase a data transmission rate by expanding a channel capacity, and is most effectively applied as 5G.
However, the millimeter wave MIMO system in the present stage is a system generally implemented by multiple lenses, and has the disadvantages of large size and weak partial channel signals, for example, as shown in fig. 1a, a 2 × 2MIMO system (i.e. 2 transmitting and 2 receiving, and 1 receiving and 1 transmitting being one antenna pair, which is the minimum unit in which a radio frequency system can normally operate) formed by general lenses has two channels with weak signals.
In electronic countermeasure, high-power electromagnetic beams are often required to be generated, the existing space power synthesis technology often adopts the millimeter wave power synthesis technology, and the gold-plated waveguide and the complex power sub-network are often adopted, so that the cost is high and the loss is large.
Therefore, there is an urgent need to develop a technology capable of solving the above technical problems.
Disclosure of Invention
The invention aims to provide a reflecting super surface for millimeter wave MIMO and space power synthesis, aiming at the technical defects in the prior art.
To this end, the invention provides a reflective super-surface for millimeter wave MIMO and spatial power synthesis, comprising a square reflective super-surface body;
the reflection-type super-surface main body comprises NxN reflection-type super-surface units; n is an integer greater than 2;
each reflective super-surface unit comprises a first metal patch, a first dielectric substrate and a first metal back plate which are sequentially arranged from top to bottom and is of a three-layer structure;
the first metal patch is a square metal patch;
a first metal patch is arranged on the top surface of the first dielectric substrate;
the whole bottom surface of the first dielectric substrate is covered with a first metal back plate;
and for each reflection type super-surface unit on different positions of the reflection type super-surface main body, the reflection phase response of the reflection type super-surface unit meets the preset caliber phase distribution condition.
Preferably, the reflective super-surface body comprises 15 × 15 reflective super-surface units.
Preferably, for each reflective super-surface unit at different positions of the reflective super-surface body, the preset aperture phase distribution condition, that is, the phase distribution corresponding to the size of the first metal patch, should satisfy the following formula (1):
wherein the content of the first and second substances,
reflecting phase responses of the reflecting super-surface units of the reflecting super-surface main body at the m-th row and the n-th column under the excitation of the feed source;
wherein m is 1,2,3 …, N; n is 1,2,3 …, N.
Preferably, the first and second electrodes are formed of a metal,
the phase response is formed by adding two parts of phase responses;
in which a part of the phase response
Odd rows are all 0 degrees, even rows are all 180 degrees;
phase response of another part
Is given by the parabolic focusing principle, which is expressed as the following equation (2):
wherein (x, y) represents the relative position of each reflective super-surface unit, λ represents the wavelength in free space, and F is the focal length;
the focal length F is 12 λ.
Preferably, the first dielectric substrate is a F4B microwave high-frequency dielectric substrate with a dielectric constant of 2.65
The first metal patch and the first metal back plate are made of copper;
the shape and size of each first metal back plate are the same as those of the first dielectric substrate.
Preferably, a second feed source and a first feed source are respectively arranged right above the left end and the right end of the reflection-type super-surface main body;
the second feed source and the first feed source are distributed in bilateral symmetry.
Preferably, the first feed source and the second feed source both adopt patch antennas;
the patch antenna comprises a second metal patch, a second dielectric substrate and a second metal back plate which are sequentially arranged from top to bottom, and is of a three-layer structure;
a second metal back plate is covered on the whole bottom surface of the second dielectric substrate;
a rectangular second metal patch is arranged at the center of the top surface of the second dielectric substrate and serves as a radiation metal sheet;
the middle part of the front end of the top surface of the second dielectric substrate is provided with microstrip lines which are longitudinally distributed;
the rear end of the microstrip line is connected with the middle position of the front side of the second metal patch;
the top surface of the second dielectric substrate is provided with a first circular through hole and a second circular through hole on the left side and the right side of the microstrip line respectively;
the central point of the first circular through hole is in a vertical distance with the microstrip line), which is equal to the vertical distance between the central point of the second circular through hole and the microstrip line;
the first round through hole and the second round through hole are respectively used for connecting an SMA connector.
Preferably, the locations of the first feed and the second feed need to satisfy the following conditions, specifically as follows:
the first feed and the second feed use a point source antenna to excite the super surface, and the far field function of the reflective super surface should be:
wherein, θ and
respectively representing a pitch angle and an azimuth angle,
reflecting phase responses corresponding to the m-th row and n-th column of the reflecting super-surface unit of the reflecting super-surface main body under the excitation of the feed source; l is the distance between adjacent reflective super-surface units;
wherein m is 1,2,3 …, N; n is 1,2,3 …, N.
Preferably, the first and second substrates are, among others,
the device comprises two parts, wherein one part is the reflection phase of each reflection type super surface unit, and the other part is the phase difference generated by the distance between a feed source and the super surface unit;
by giving
The directivity function of the reflective metasurface should be:
compared with the prior art, the reflection type super surface for millimeter wave MIMO and space power synthesis is scientific in design, electromagnetic beams with different incident directions can be reflected by the same reflection type super surface to generate reflection beams in the same direction, flexible regulation and control of the electromagnetic waves are verified, and the reflection type super surface has great practical significance.
By applying the invention, after the MIMO system is formed, the signal of each channel in the MIMO system can be stronger, the problem that the signal of part of the channels is weaker in the existing millimeter wave MIMO system is solved, and the invention has great practical significance.
In addition, the invention can effectively reduce the loss of the MIMO system and improve the gain of the electromagnetic wave in the MIMO system.
In addition, the invention is beneficial to reducing the overall size of the MIMO system and reducing the hardware cost required by generating high-power electromagnetic beams.
Drawings
Fig. 1a is a schematic diagram of a channel distribution of a conventional 2 × 2MIMO system composed of general lenses;
FIG. 1b is a schematic diagram of a reflection-type super-surface for millimeter wave MIMO and spatial power synthesis according to the present invention, with a channel distribution;
FIG. 2a is a graph showing the reflected phase response of a one-bit super-surface, i.e., the reflected phase difference between two adjacent units is 180 °;
FIG. 2b is a graph of the reflected phase response calculated by the parabolic focusing principle;
FIG. 2c is a reflection phase response profile obtained by adding FIG. 2a and FIG. 2b, i.e. a reflection phase response profile of a reflective super-surface provided by the present invention;
FIG. 3 is a schematic diagram of the overall position distribution of a reflective super-surface and two feed sources for millimeter wave MIMO and spatial power synthesis provided by the present invention, and the diagram is a top view;
FIG. 4a is a graph of the location and directionality of a feed;
FIG. 4b is a diagram of a theoretical model for feed excitation;
FIG. 5 is a schematic diagram of a single feed patch antenna configuration for use with the present invention;
FIG. 6 is a two-dimensional pattern at 26GHz for a single feed patch antenna employed in the present invention;
FIG. 7 is a schematic structural diagram of each reflective super-surface unit in a reflective super-surface for millimeter wave MIMO and spatial power synthesis according to the present invention;
FIG. 8 is a diagram showing simulation results of reflection phase response of each reflection super-surface unit at 26GHz in a reflection super-surface for millimeter wave MIMO and spatial power synthesis provided by the invention;
FIG. 9 is a schematic structural diagram of a reflective super-surface for millimeter wave MIMO and spatial power synthesis according to the present invention;
FIG. 10 is the pattern of the overall model at 26GHz when the first feed is excited alone;
FIG. 11 is the 26GHz directional diagram of the overall model when the second feed is excited alone;
FIG. 12 is the 26GHz directional diagram of the overall model when two feeds are excited simultaneously;
FIG. 13 is a schematic diagram of a comparison between a simulation and an actual measurement | S11| normalized at 22GHz to 30GHz for an actual measurement model formed by a first feed source and a reflective super-surface provided by the present invention;
FIG. 14 is a schematic diagram showing a comparison of simulated and measured E-plane patterns normalized at 26GHz for a measured model consisting of a first feed and a reflective metasurface provided by the present invention;
FIG. 15 is a schematic diagram showing a comparison between simulated and measured H-plane directional patterns normalized at 26GHz of a measured model formed by a first feed source and a reflective metasurface provided by the present invention.
Detailed Description
In order that those skilled in the art will better understand the technical solution of the present invention, the following detailed description of the present invention is provided in conjunction with the accompanying drawings and embodiments.
Referring to fig. 1b to 15, the present invention provides a reflective super-surface for millimeter wave MIMO and spatial power synthesis, comprising a square reflective super-surface body 100;
a reflective super-surface body 100 comprising nxn reflective super-surface units 200; n is an integer greater than 2; for example, it is preferable that: 15 x 15 reflective super-surface units 200 (225 total, i.e., 15 in each row and 15 in each column);
as shown in fig. 7, each reflective super-surface unit 200 includes a first metal patch 201, a first dielectric substrate 202, and a first metal back plate, which are sequentially arranged from top to bottom, and is a three-layer structure;
a first metal patch 201 which is a square metal patch;
a top surface of the first dielectric substrate 202, provided (e.g. by printing) with a first metal patch 201;
the whole bottom surface of the first dielectric substrate 202 is covered with a first metal back plate;
wherein, for each reflective super-surface unit 200 at different positions of the reflective super-surface body 100, the reflective phase response thereof meets the preset aperture phase distribution condition.
In the present invention, for the specific implementation, for the present invention, the reflected phase response distribution calculation process of the reflective super surface is shown in fig. 2a to 2c, where fig. 2a is a reflected phase response distribution diagram of a one-bit super surface, that is, the reflected phase difference between two adjacent reflective super surface units is 180 °; FIG. 2b is a graph of the reflected phase response calculated by the parabolic focusing principle; fig. 2c is a reflection phase response distribution diagram obtained by adding fig. 2a and fig. 2b, namely, a reflection phase response distribution diagram of the reflective super-surface provided by the present invention.
In the present invention, in a specific implementation, the reflective super-surface is composed of 15 × 15 reflective super-surface units, and for each reflective super-surface unit 200 at different positions of the reflective super-surface body 100, the phase distribution of the preset aperture phase distribution condition (specifically, the size of the first metal patch 201 thereon) should satisfy the following formula (1):
wherein the content of the first and second substances,
(i.e., the phase distribution in fig. 2C) shows the reflected phase response of the reflective super-surface body 100 under the excitation of the feed source in the reflective super-surface unit 200 at the m (m is 1,2,3 …, N) th row and N (N is 1,2,3 …, N) th column. For 15 × 15 reflective super surface units 200, N is 15;
in the concrete implementation aspect, the method comprises the following steps of,
the phase response is formed by adding two parts of phase responses;
in which a part of the phase response
(i.e., phase distribution of FIG. 2A) is full of odd columns0 degrees and all even rows are 180 degrees;
phase response of another part
(i.e., the phase profile of fig. 2B), which follows the principle of parabolic focusing, is expressed as the following equation (2):
where (x, y) denotes the relative position of each reflective super-surface unit 200, λ denotes the wavelength in free space, and F is the focal length (where the focal length F is 12 λ).
In a specific implementation of the present invention, as shown in fig. 7, the side length m of each reflective super-surface unit is 12 mm.
In concrete implementation, the material of the first metal patch 201 is copper, and the thickness is 0.018mm, wherein the side length n of the first metal patch 201 has a value range of: n is more than or equal to 0.1mm and less than or equal to 12mm, and the step length of the first metal patch 201 shown in FIG. 7 is 1 mm.
It should be noted that, with the present invention, the reflection phase response of the reflective super-surface unit where the metal patch is located is determined by the size of the square metal patch (i.e., the first metal patch 201).
In concrete implementation, the first dielectric substrate 202 as the intermediate layer is a common microwave high-frequency dielectric substrate, for example, an F4B microwave high-frequency dielectric substrate with a dielectric constant of 2.65, and the thickness h is 1.964 mm.
In particular, the first metal back plate is made of copper, is 0.018mm thick and covers the back face of the whole reflective super-surface unit. The size and shape of each first metal back plate are the same as those of the first dielectric substrate 202.
It should be noted that, for the present invention, the reflective super-surface is composed of 15 × 15 reflective super-surface units 200, each reflective super-surface unit 200 uses an F4B high-frequency plate (F4B is not metal) with a dielectric constant of 2.65 as a dielectric substrate (i.e., a first dielectric substrate), the upper layer of the dielectric substrate is a square metal patch (i.e., a first metal patch) and is made of metal copper, and the lower layer of the dielectric substrate is copper (i.e., a first metal back plate) with the same size as the dielectric substrate and is grounded.
For the present invention, each reflective super-surface unit has an effect of reflecting electromagnetic waves. The first metal patches of the plurality of reflective super-surface units can be an integral copper sheet, namely, the first metal patches are integrally formed; the first dielectric substrate of the plurality of reflective super-surface units may be a unitary dielectric substrate, i.e. integrally formed. The size of the individual reflective super-surface units, in particular only the first metal patch 201). Wherein, the size of the first metal patch 201) is used to determine the reflection phase response of the reflective super-surface unit where the metal patch is located.
In the present invention, in terms of specific implementation, referring to fig. 3, a second feed source 302 and a first feed source 301 are respectively disposed right above the left and right ends of the reflective super-surface main body 100;
the second feed 302 and the first feed 301 are distributed symmetrically.
It should be noted that, for the present invention, the first feed 301 and the second feed 302 are symmetrically disposed to radiate electromagnetic waves directed to the central position of the reflective super-surface body 100.
For the present invention, the reflective super-surface includes 15 × 15 reflective super-surface units with different size parameters (specifically, the size parameters of the first metal patch 201 are different, and the size parameters of the first dielectric substrate 202 and the first metal back plate are the same), the reflective super-surface units are arranged according to the reflection phase responses of the reflective super-surface units at different positions, and according to the predetermined function, the type of the feed source is selected and the distance between the reflective super-surface main body 100 and the feed source is determined, so that the reflective super-surface main body 100 respectively regulates and controls the wave fronts of the reflected electromagnetic waves as required under the excitation of the electromagnetic waves in two different directions to realize the predetermined function.
In a specific implementation, considering that the side length m of each reflective super-surface unit is 12mm, the overall side length of the reflective super-surface body 100 is 12 × 15mm, which is equal to 180 mm.
As shown in fig. 9, which is a schematic structural diagram of the reflective super-surface provided by the present invention, the overall side length p of the reflective super-surface main body 100 is 180mm, which is a total of three layers. The upper layer metal patch is a metal patch (i.e., a first metal patch 201) with a length of side specifically taking a value, and the length of the side is determined according to a reflection phase response distribution diagram of the reflection-type super surface shown in fig. 2a to 2c and a reflection phase response simulation result diagram of the reflection-type super surface unit shown in fig. 8 at 26GHz, wherein the metal patch is made of copper and has a thickness of 0.018 mm; the first dielectric substrate 202 of the intermediate layer is an F4B microwave high-frequency dielectric substrate, and the thickness h is 1.964 mm; the first metal back plate of the lower layer is copper, has a thickness of 0.018mm, and covers the entire back surface of the reflective super-surface main body 100.
In particular, referring to fig. 3, the first feed source 301 and the second feed source 302 are both patch antennas, and according to a given function, the center of the reflective super-surface main body 100 is placed at the origin of coordinates (0, 0, 0), the first feed source 301 is placed at the coordinates (70mm, 0, 115mm), and the second feed source 302 is placed at the coordinates (-70mm, 0, 115mm), so that the reflective super-surface main body 100 respectively regulates and controls the wavefront of the reflected electromagnetic wave as required under the excitation of the electromagnetic wave in two different directions to realize the given function.
The center of the reflective super-surface body 100 is set as the origin of coordinates, and a three-dimensional rectangular coordinate system is established, wherein the three-dimensional rectangular coordinate system is a three-dimensional cartesian coordinate system, the X-axis direction is a transverse linear direction, the Y-axis direction is a longitudinal linear direction, and the Z-axis direction is a vertical direction; the coordinates of the center of the reflective super surface are (0mm,0mm,0mm), the reflective super surface main body 100 is placed on an XOY plane, the two feeds, namely the first feed 301 and the second feed 302, are placed on an XOZ plane, the coordinates of the first feed 301 are (70mm, 0, 115mm), the coordinates of the second feed 302 are (-70mm, 0, 115mm), and the radiation directions of the two feeds, namely the first feed 301 and the second feed 302, point to the center of the super surface (0mm,0mm,0mm), as shown by a dotted line in fig. 3.
The intended function, which is intended to be performed by the reflective super-surface body 100, is a function commonly used in the electromagnetic field, such as beam forming, far-field beam scanning, radar cross-section reduction, etc., compared to the far field.
In a concrete implementation, the two feed sources, namely the first feed source 301 and the second feed source 302, have a vertical distance F from the reflective super-surface main body 100, that is, a focal length of the reflective super-surface is F, the focal length is set according to a set function of the reflective super-surface, when the super-surface performs wavefront control on electromagnetic waves radiated by the feed sources, the focal length F is determined according to a geometrical optics phase compensation principle (for example, the focal length F is equal to 12 λ, and λ represents a wavelength in a free space). The feed source is selected according to the set function of the reflective super surface, when the reflective super surface performs wave front regulation on electromagnetic waves radiated by the feed source, the patch antenna with wide lobe width is selected as the feed source.
As shown in fig. 4a, a relation graph of the position and the directivity size of the feed source is obtained, a theoretical model of the reflective super-surface is established by using MATLAB, the theoretical model is placed on an xoy plane, the feed source at different positions of the plane where y is 0 is simulated, a relation between the directivity and the feed source position is obtained, and two optimal positions of the feed source when the directivity is maximum are determined to be (6, 0, 10) and (-6, 0, 10), respectively.
As shown in fig. 4b, the feed source is placed in the (6, 0, 10) direction diagram of the theoretical model, and since the theoretical model of the reflective super-surface is placed in the xoy plane, it can be seen that the main radiation direction of the direction diagram of the theoretical model is perpendicular to the theoretical model.
In specific implementation, how to determine the locations of the feeds (the first feed 301 and the second feed 302), that is, the locations of the first feed 301 and the second feed 302, needs to satisfy the following conditions, which are specifically as follows:
using a point source antenna as a feed (i.e., as the first feed 301 and the second feed 302) to excite the super-surface, the far-field function of the reflective super-surface should be:
wherein, θ and
respectively representing a pitch angle and an azimuth angle,
the reflection phase response of the reflection type super surface unit 200 in the mth row and the nth column of the reflection type super surface main body 100 is shown under the excitation of the feed source; l is the distance between adjacent reflective super-surface units 200;
wherein the content of the first and second substances,
two parts are included, one part is the reflection phase of each reflection type super surface unit 200, and the other part is the phase difference generated by the distance between the feed source and the super surface unit; by giving
Obtaining a given reflective super-surface directional diagram, wherein the directional function of the reflective super-surface is as follows:
for the specific implementation of the invention, a theoretical model is established by using MATLAB, the theoretical model is placed on an xoy plane, the feed sources positioned at different positions of a plane y-0 are simulated to obtain the relationship between the directivity and the position of the feed source, two optimal positions (namely the positions of the feed sources) of the feed sources when the directivity is maximum are determined, the feed sources are placed at the optimal positions, and as shown in figure 4a, electromagnetic waves emitted by the feed sources have the maximum gain after being reflected by a reflective super surface.
As shown in fig. 5, it is a simulation model diagram of patch antenna as a feed (first feed 301 or second feed 302).
Referring to fig. 5, a first feed 301 and a second feed 302 are used as feeds, and both adopt patch antennas;
the patch antenna comprises a second metal patch 401, a second dielectric substrate 402 and a second metal back plate which are sequentially arranged from top to bottom, and is of a three-layer structure;
the whole bottom surface of the second dielectric substrate 402 is covered with a second metal back plate;
a rectangular second metal patch 401 is disposed (for example, by printing) at the center of the top surface of the second dielectric substrate 402, and the second metal patch 401 is used as a radiating metal sheet;
the middle part of the front end of the top surface of the second dielectric substrate 402 is provided with microstrip lines 403 which are longitudinally distributed (for example, by printing);
the rear end of the microstrip line 403 is connected with the middle position of the front side of the second metal patch 401;
a first circular through hole 404 and a second circular through hole 405 are respectively formed in the left side and the right side of the microstrip line 403 on the top surface of the second dielectric substrate 402;
the vertical distance between the center point of the first circular through hole 404 and the microstrip line 403 is equal to the vertical distance between the center point of the second circular through hole 405 and the microstrip line 403.
In specific implementation, the first circular through hole 404 and the second circular through hole 405 are respectively used for connecting one SMA joint (two SMA joints in total).
Note that the SMA connector is used to provide excitation to the antenna (i.e., the feed patch antenna 8). The SMA connector is known by the name Sub Miniature version a and is a typical high frequency connector. The SMA connector has the characteristics of small size, high reliability, wide frequency band, excellent performance, long service life and the like, so the SMA connector is suitable for connecting a radio frequency cable or a microstrip line in a radio frequency loop of microwave equipment and a digital communication system.
In the specific implementation, the diameter d of the first circular through hole 404 and the second circular through hole 405 is 2mm, and the first circular through hole and the second circular through hole are used for connecting the SMA adapter.
It should be noted that the patch antenna is fed by the microstrip line 403, and the first circular through hole 404 and the second circular through hole 405 are used for connecting the SMA adapter, so as to adjust the center frequency of the antenna to about 26 GHz.
In specific implementation, the second metal patch 401 on the upper layer is a rectangular metal patch made of copper and having a thickness of 0.018mm, wherein the length a of the second metal patch 401 is 4.5mm, and the width b of the second metal patch is 3.4 mm;
in a concrete implementation, the second dielectric substrate 402 as the middle layer is a Ruilong microwave high-frequency dielectric substrate, and the thickness is 0.762 mm;
in the concrete implementation, the second metal back plate of the lower layer is made of copper, the thickness of the second metal back plate is 0.018mm, and the second metal back plate covers the back face of the whole unit.
It should be noted that, for the present invention, the patch antennas as the first feed 301 and the second feed 302 are square in shape, and the side length l is 14 mm.
In the specific implementation, the second metal patch 401 and the microstrip line 403 are made of copper, and the radiator of the patch antenna is generally made of copper, because the price is low, the radiation characteristic is good.
As shown in fig. 6, the two-dimensional pattern of the patch antenna as the feed at 26GHz is shown, the maximum gain of the antenna is 7.17dBi, and as can be seen from the figure, the patch antenna has a wide lobe width and is suitable for being used as a reflective super-surface feed. The design of the invention is only suitable for two feed sources adopting patch antennas, and the installation positions and angles are shown in figure 3.
Fig. 8 is a simulation result diagram of the reflection phase response of the reflective super-surface unit at 26GHz according to the present invention, and fig. 8 is a simulation result diagram of the relationship between the reflection phase response of the reflective super-surface unit at 26GHz and the unit side length n.
Referring to fig. 8, the reflective super-surface unit provided by the present invention has a reflective phase response covering a range of-180 ° to 180 ° as a function of the side length of the upper square metal patch (i.e. the first metal patch). According to the phase distribution shown in fig. 2c, the reflection phase response of the reflection-type super-surface unit at the corresponding position of the reflection-type super-surface is determined, and further the side length n of the unit at the corresponding position is determined (the side length n of the reflection-type super-surface unit is different only by the upper square metal patch, and the material sizes of the rest middle dielectric plate and the lower metal copper are all the same). The reflection phase response of each reflection type super surface unit is different, the regulation and control capability of the electromagnetic waves is also different, and the whole reflection type super surface can realize the beam steering and beam shaping effects on the electromagnetic waves in different directions under the reflection phase response distribution of fig. 2C.
As shown in fig. 10, when the first feed source 301 is excited alone, the overall pattern is a directional diagram at 26GHz, and it can be seen that, after the electromagnetic wave radiated by the patch antenna as the feed source is reflected by the reflective super-surface of the present invention, the overall radiation direction is perpendicular to the reflective super-surface, and beam forming is realized, and the maximum gain is 11.8 dBi.
As shown in fig. 11, when the second feed source 302 is excited alone, the overall model is the directional diagram at 26GHz, and it can be seen that, after the electromagnetic wave radiated by the patch antenna serving as the feed source is reflected by the reflective super-surface provided by the present invention, the overall radiation direction is perpendicular to the reflective super-surface, and beam forming is realized, and the maximum gain is 11.8 dBi.
As shown in fig. 10 and 11, the reflective super-surface provided by the present invention respectively adjusts and controls the wavefront of the reflected electromagnetic wave as required under the excitation of the electromagnetic waves radiated by the first feed source 301 and the second feed source 302 in two different directions, so that the electromagnetic beams with different incident directions are reflected by the same reflective super-surface, and the reflected beams in the same direction are generated. When the first feed 301 and the second feed 302 are independent of each other, and the reflective super-surface provided by the present invention as a whole, a MIMO antenna as shown in fig. 3 is formed.
As shown in fig. 12, when the first feed source 301 and the second feed source 302 are excited simultaneously, the overall model has a directional diagram at 26GHz, and it can be seen that the electromagnetic waves radiated by the first feed source 301 and the second feed source 302 are perpendicular to the reflective super surface after being reflected by the reflective super surface provided by the present invention, and beam forming is realized, the maximum gain is 14.9dBi, compared with the reflection result of a single feed source, the maximum gain is increased by 3dBi, which indicates that the overall radiation directions are superposed, and spatial power synthesis is realized.
In order to further verify the feasibility of the reflective super surface for millimeter wave MIMO and space power synthesis provided by the invention, the reflective super surface is processed by adopting a PCB process, and the result of the first feed source 301 is tested and verified in a darkroom.
Based on the above-mentioned reflective super surface provided by the present invention, referring to fig. 3, the present invention further provides an electromagnetic wave enhancement model for the application of the reflective super surface, comprising: the reflective super-surface body 100 shown in fig. 9, and a first feed 301 and a second feed 302 using patch antennas;
the second feed source 302 and the first feed source 301 are respectively located right above the left end and the right end of the reflective super-surface main body 100 (for example, right above the middle position of the left end and the right end);
the electromagnetic wave enhancement model comprises two SMA adapter connectors, wherein the two SMA adapter connectors are respectively connected with a first feed source 301 and a second feed source 302 and are used for supplying power to the first feed source 301 and the second feed source 302 which adopt patch antennas;
in a specific implementation, the first feed source 301 and the second feed source 302 may be supported by two brackets located at the left and right sides of the reflective super-surface main body 100.
The electromagnetic waves radiated by the first feed source 301 and the second feed source 302 are directed to the center of the reflective super surface, and the electromagnetic waves are emitted from the center of the reflective super surface after being emitted by the reflective super surface and are perpendicular to the plane of the reflective super surface.
It should be noted that, as shown in fig. 3, the first feed 301 and the second feed 302 of the patch antenna are used to implement the functions of beam steering and beam forming after being reflected by the reflective super-surface main body 100. If the first feed source 301 and the second feed source 302 are separately excited, the feed source of the patch antenna and the reflective super surface jointly form an MIMO antenna, and the MIMO antenna can be applied to an MIMO system; if two feed sources of the patch antenna are adopted for simultaneous excitation, electromagnetic waves radiated by the first feed source 301 and the second feed source 302 are superposed in space after being reflected by the reflective super surface, and space power synthesis is realized.
As shown in fig. 13, for the measured model formed by the first feed source and the reflective super-surface provided by the present invention, the simulation and the measured | S11| normalized at 22GHz to 30GHz are compared, and due to the influence of the test environment, the error is within the allowable range, the simulation and the test result are both resonant at 26GHz, and the curves are substantially matched.
As shown in fig. 14, the simulated and actual measured E-plane directional patterns normalized at 26GHz for the actual measurement model formed by the first feed source and the reflective super-surface provided by the present invention are compared; as shown in fig. 15, the simulated and actual H-plane directional patterns normalized at 26GHz for the actual measurement model formed by the first feed source and the reflective super surface provided by the present invention are compared; the test result is very consistent with the simulation result, the result proves the effectiveness of all simulations, and the effectiveness of the reflecting super-surface for millimeter wave MIMO and space power synthesis provided by the invention is proved.
It can be seen from fig. 14 that the difference between simulation and test of the electromagnetic wave enhancement model formed by a single feed source and the reflective super surface is within the allowable error range.
In the present invention, referring to fig. 1a and 1b, in the 2 × 2MIMO system formed by the reflective super-surface of the present invention, the signal of each channel is strong, while the existing 2 × 2MIMO system formed by general lenses has two channels with weak signals; and the electromagnetic wave radiated by the feed source realizes beam steering and beam forming after being reflected by the reflective super surface of the invention, and the gain is increased from 7.17dBi to 11.8 dBi.
Based on the technical scheme, by applying the invention, the electromagnetic beams with different incident directions are reflected by the same reflective super surface for the first time, the reflected beams in the same direction are generated, and the flexible regulation and control of the electromagnetic waves are verified.
In addition, the invention also provides a design method of the reflective super surface for MIMO and space power synthesis, which comprises the following steps:
step S1, according to the emission phase response of the given one-bit super surface (namely the reflection phase difference of two adjacent units is 180 degrees) and the parabolic focusing principle, the reflection phase distribution of the whole reflection super surface caliber is given, and the phase distribution is normalized;
step S2, extracting the reflection phase distribution of the normalized reflection-type super-surface caliber, establishing a theoretical model by using MATLAB, and verifying MIMO and space power synthesis;
step S3, designing a reflective super-surface unit by CST MWS electromagnetic simulation software, and determining the size parameter of each reflective phase response unit;
step S4, selecting and arranging super surface unit structures with corresponding sizes according to the normalized reflection phase distribution of the super surface caliber, obtaining the integral structure of the reflection type super surface, and establishing a simulation model;
step S5, according to the established function, selecting the feed source type and the distance from the feed source to the reflective super surface, symmetrically placing the two feed sources (namely the first feed source 301 and the second feed source 302), and verifying the MIMO and space power synthesis.
In particular implementation, step S1 is specifically as follows:
first, assuming that the reflective super-surface is composed of 15 × 15 (i.e. N is 15) super-surface units with different size parameters, the phase distribution of the aperture should be:
wherein the content of the first and second substances,
the reflecting super-surface unit of the reflecting super-surface in the m (m is 1,2,3 … 15) th row and the n (n is 1,2,3 … 15) th column under the excitation of the feed source has a reflecting phase response which is formed by adding two parts of phase responses, wherein one part of phase responses are phase responses
The odd rows are all 180 degrees, and the even rows are all 0 degrees; another part of the phase response
Obey the parabolic focusing principle, which is expressed as:
where (x, y) denotes the relative position of each super-surface element, λ denotes the wavelength in free space, and F is the focal length.
In a specific implementation, a point source antenna is used as a feed source to excite the reflective super surface, and then a far field function of the reflective super surface is as follows:
wherein, θ and
respectively representing a pitch angle and an azimuth angle,
reflecting phase responses corresponding to the cells in the m row and the n column of the reflecting super surface under the excitation of the feed source are represented; l is the distance between adjacent reflective super-surface units;
the device comprises two parts, wherein one part is the reflection phase of each reflection type super surface unit, and the other part is the phase difference generated by the distance between a feed source and the reflection type super surface unit; by giving
Obtaining a given super-surface directional diagram, wherein the directivity function of the super-surface is as follows:
in particular implementation, step S2 is specifically as follows:
the method comprises the steps of establishing a theoretical model by using MATLAB, placing the theoretical model on an xoy plane, simulating feed sources located at different positions of a plane where y is 0 to obtain the relationship between directivity and the position of the feed sources, determining two optimal positions of the feed sources when the directivity is maximum, placing the two feed sources at the two optimal positions respectively, and when the two feed sources are excited respectively, verifying MIMO (multiple input multiple output) and when the two feed sources are excited together, verifying spatial power synthesis.
Based on the technical scheme, for the reflective super surface provided by the invention, the wave front regulation and control can be performed on the electromagnetic wave radiated by the feed source through the reflective super surface, and the functions of beam steering and beam forming are realized, so that a plurality of feed sources (such as a plurality of feed source patch antennas) can realize millimeter wave MIMO and space power synthesis through sharing a single-port surface (namely the reflective super surface provided by the invention).
The reflecting super surface provided by the invention is a reflecting super surface applied to MIMO and space power synthesis and consists of a plurality of super surface units with different reflecting phase responses. Under the excitation of a given incident electromagnetic wave, the super surface can independently regulate and control the electromagnetic wave. Due to the characteristics of the reflection-type super surface, the reflection-type super surface is used for flexibly regulating and controlling electromagnetic waves in different directions, and can be efficiently applied to MIMO and space power synthesis.
Compared with the prior art, the invention has the following advantages:
1. the design science: the reflective super-surface adopts the square metal patches with different sizes as the reflective super-surface units and the patch antenna as the feed source, and has scientific design, convenience and quickness.
2. Rational in infrastructure, low cost: the invention has low precision requirement, can be processed by adopting a PCB process, and has low processing difficulty and low cost.
3. The section is low: the reflective super surface is of a single-layer structure, has a low section, is easy to integrate and has wide application scenes.
In summary, compared with the prior art, the reflective super surface for millimeter wave MIMO and spatial power synthesis provided by the invention has a scientific design, can reflect electromagnetic beams with different incident directions through the same reflective super surface to generate reflected beams in the same direction, verifies that the electromagnetic waves are flexibly regulated and controlled, and has great practical significance.
By applying the invention, after the MIMO system is formed, the signal of each channel in the MIMO system can be stronger, the problem that the signal of part of the channels is weaker in the existing millimeter wave MIMO system is solved, and the invention has great practical significance.
In addition, the invention can effectively reduce the loss of the MIMO system and improve the gain of the electromagnetic wave in the MIMO system.
In addition, the invention is beneficial to reducing the overall size of the MIMO system and reducing the hardware cost required by generating high-power electromagnetic beams.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A reflective super-surface for millimeter-wave MIMO and spatial power combining, comprising a square reflective super-surface body (100);
a reflective super-surface body (100) comprising N x N reflective super-surface units (200); n is an integer greater than 2;
each reflective super-surface unit (200) comprises a first metal patch (201), a first dielectric substrate (202) and a first metal back plate which are sequentially arranged from top to bottom and are of a three-layer structure;
a first metal patch (201) which is a square metal patch;
the top surface of the first dielectric substrate (202) is provided with a first metal patch (201);
the whole bottom surface of the first dielectric substrate (202) is covered with a first metal back plate;
wherein, for each reflection type super-surface unit (200) on different positions of the reflection type super-surface main body (100), the reflection phase response thereof conforms to the preset caliber phase distribution condition.
2. The reflective super surface of claim 1, wherein the reflective super surface body (100) comprises 15 x 15 reflective super surface units (200).
3. The reflective super-surface according to claim 1, wherein the predetermined aperture phase distribution condition, i.e. the phase distribution corresponding to the size of the first metal patch (201), for each reflective super-surface unit (200) at different positions of the reflective super-surface body (100) satisfies the following formula (1):
wherein the content of the first and second substances,
the reflection type super-surface unit (200) of the reflection type super-surface main body (100) at the m-th row and n-th column positions reflects the phase response under the excitation of the feed source;
wherein m is 1,2,3 …, N; n is 1,2,3 …, N.
4. The reflective super surface of claim 3,
the phase response is formed by adding two parts of phase responses;
in which a part of the phase response
Odd rows are all 0 degrees, even rows are all 180 degrees;
phase response of another part
Is given by the parabolic focusing principle, which is expressed as the following equation (2):
wherein (x, y) represents the relative position of each reflective super-surface unit (200), λ represents the wavelength in free space, and F is the focal length;
the focal length F is 12 λ.
5. The reflective super surface of claim 1, wherein the first dielectric substrate (202) is a F4B microwave hf dielectric substrate having a dielectric constant of 2.65
The first metal patch (201) and the first metal back plate are made of copper;
the shape and size of each first metal back plate are the same as those of the first dielectric substrate (202).
6. The reflective super-surface according to claim 1, wherein a second feed source (302) and a first feed source (301) are respectively arranged right above the left end and the right end of the reflective super-surface main body (100);
the second feed source (302) and the first feed source (301) are symmetrically distributed left and right.
7. A reflective super-surface according to claim 6, wherein the first feed (301) and the second feed (302) are each a patch antenna;
the patch antenna comprises a second metal patch (401), a second dielectric substrate (402) and a second metal back plate which are sequentially arranged from top to bottom, and is of a three-layer structure;
the whole bottom surface of the second dielectric substrate (402) is covered with a second metal back plate;
a rectangular second metal patch (401) is arranged at the center of the top surface of the second dielectric substrate (402), and the second metal patch (401) is used as a radiating metal sheet;
the middle part of the front end of the top surface of the second dielectric substrate (402) is provided with microstrip lines (403) which are distributed longitudinally;
the rear end of the microstrip line (403) is connected with the middle position of the front side of the second metal patch (401);
a first circular through hole (404) and a second circular through hole (405) are respectively formed in the left side and the right side of the microstrip line (403) on the top surface of the second dielectric substrate (402);
the vertical distance between the central point of the first circular through hole (404) and the microstrip line (403) is equal to the vertical distance between the central point of the second circular through hole (405) and the microstrip line (403);
the first round through hole (404) and the second round through hole (405) are respectively used for connecting an SMA joint.
8. A reflective metasurface according to claim 6, wherein the positions of the first feed (301) and the second feed (302) are such that the following conditions are fulfilled:
the first feed (301) and the second feed (302) use point source antennas to excite the super-surface, the far field function of the reflective super-surface should be:
wherein, θ and
respectively representing a pitch angle and an azimuth angle,
the reflection phase response of the reflection type super surface unit (200) of the m-th row and the n-th column of the reflection type super surface main body (100) is shown under the excitation of a feed source; l is the distance between adjacent reflective super-surface units (200);
wherein m is 1,2,3 …, N; n is 1,2,3 …, N.
9. The reflective super surface of claim 8,
Includedtwo parts, one part is the reflection phase of each reflection type super surface unit (200) and the other part is the phase difference generated by the distance between the feed source and the super surface unit;
by giving
The directivity function of the reflective metasurface should be:
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